Peter C. Chua

CX-4945, an Orally Bioavailable Selective Inhibitor of Protein Kinase CK2, Inhibits Prosurvival and Angiogenic Signaling and Exhibits Antitumor Efficacy

Malignant transformation and maintenance of the malignant phenotype depends on oncogenic and non-oncogenic proteins that are essential to mediate oncogene signaling and to support the altered physiologic demands induced by transformation. Protein kinase CK2 supports key prosurvival signaling pathways and represents a prototypical non-oncogene. In this study, we describe CX-4945, a potent and selective orally bioavailable small molecule inhibitor of CK2. The antiproliferative activity of CX-4945 against cancer cells correlated with expression levels of the CK2α catalytic subunit. Attenuation of PI3K/Akt signaling by CX-4945 was evidenced by dephosphorylation of Akt on the CK2-specific S129 site and the canonical S473 and T308 regulatory sites. CX-4945 caused cell-cycle arrest and selectively induced apoptosis in cancer cells relative to normal cells. In models of angiogenesis, CX-4945 inhibited human umbilical vein endothelial cell migration, tube formation, and blocked CK2-dependent hypoxia-induced factor 1 alpha (HIF-1α) transcription in cancer cells. When administered orally in murine xenograft models, CX-4945 was well tolerated and demonstrated robust antitumor activity with concomitant reductions of the mechanism-based biomarker phospho-p21 (T145). The observed antiproliferative and anti-angiogenic responses to CX-4945 in tumor cells and endothelial cells collectively illustrate that this compound exerts its antitumor effects through inhibition of CK2-dependent signaling in multiple pathways. Finally, CX-4945 is the first orally bioavailable small molecule inhibitor of CK2 to advance into human clinical trials, thereby paving the way for an entirely new class of targeted treatment for cancer.

A new method for the conversion of secondary and tertiary amides to bridged orthoesters

Abstract Secondary and tertiary amides were treated with trifluoromethanesulfonic (triflic) anhydride in the presence of pyridine at low temperatures to generate imino and iminium triflates. Successive treatment with 2,2-bishydroxymethyl-1-propanol in the pyridine buffered solution gave the corresponding 2,6,7-trioxabicyclo[2.2.2]octane orthoesters in good to excellent yields at below room temperature.

THIOLYSIS AND HYDROLYSIS OF IMINO AND IMINIUM TRIFLATES : SYNTHESIS OF SECONDARY AND TERTIARY THIOAMIDES AND 18O-LABELED AMIDES

Secondary and tertiary amides were treated with trifluoromethanesulfonic (triflic) anhydride in the presence of pyridine at low temperatures to generate imino and iminium triflates. Subsequent treatment with hydrogen sulfide immediately gave rise to the corresponding thioamide in good to excellent yields at low temperature. Alternatively, treatment with stoichiometric amounts of 18O-labeled water produced the 18O-labeled amide.

Synthesis and SAR of inhibitors of protein kinase CK2: Novel tricyclic quinoline analogs

Protein kinase CK2 is a potential drug target for many diseases including cancer and inflammation disorders. The crystal structure of clinical candidate CX-4945 1 with CK2 revealed an indirect interaction with the protein through hydrogen bonding between the NH of the 3-chlorophenyl amine and a water molecule. Herein, we investigate the relevance of this hydrogen bond by preparing several novel tricyclic derivatives lacking a NH moiety at the same position. This SAR study allowed the discovery of highly potent CK2 inhibitors.

Abstract 4780: RXDX-107 exhibits multiple mechanisms of intracellular delivery and results in extensive drug-induced interstrand crosslinks in solid tumor preclinical models

RXDX-107 is a dodecanol alkyl ester of bendamustine, which is then encapsulated in human serum albumin (HSA) to form nanoparticles. Bendamustine is an alkylating agent that induces interstrand DNA crosslinks (ICLs) and causes cell death via several pathways, including intrinsic apoptosis. The activity of bendamustine in the treatment of solid tumor malignancies has not been impressive, possibly due to the pharmacokinetic and limited biodistribution properties of bendamustine. RXDX-107 was designed to improve tissue biodistribution over bendamustine, which may result in superior efficacy and tolerability in patients with solid tumors. In preclinical studies, RXDX-107 displayed significant anti-tumor activity in multiple solid tumor cell lines, cell line-derived xenograft (CDX) and patient-derived xenograft (PDX) models of advanced solid tumors, such as breast, lung, and ovarian cancer. In this study, we further evaluated the mechanism of action of RXDX-107, particularly the means of entry and accumulation of drug into tumor cells. We have developed a novel analytical method to precisely quantify both dodecanol alkyl ester of bendamustine and released bendamustine in tissue culture medium and cells. Our data demonstrate that RXDX-107 is transported into cells in three active forms. Firstly, RXDX-107 slowly releases bendamustine into the extracellular medium, and released bendamustine then enters into cells. Secondly, the dodecanol alkyl ester of bendamustine is transported into cells and causes ICLs. And lastly, by measuring macropinocytosis, we also determined that human serum albumin nanoparticles mediate the intracellular entry of RXDX-107. Each of these mechanisms results in the formation of ICLs. In addition, comet assay data demonstrate that RXDX-107 displayed stronger induction of ICLs than bendamustine, and the induced ICLs persist over 48 hours in multiple solid tumor cell lines. Taken together, our data demonstrate that RXDX-107 enters and accumulates into cells via multiple mechanisms, and causes extensive and superior ICLs compared to bendamustine in several solid tumor cell lines, thereby providing a strong rationale for further investigation of this agent in solid tumor indications. Citation Format: Leenus Martin, Roopal Patel, Michael Johnson, Jerry Cao, Peter Chua, Colin Walsh, Jennifer Oliver, Pratik Multani, Robert Wild, Ralph Lin, Gary G. Li. RXDX-107 exhibits multiple mechanisms of intracellular delivery and results in extensive drug-induced interstrand crosslinks in solid tumor preclinical models. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4780.